[Xen-devel] Re: [PATCH] C6 state with EOI issue fix for some Intel processors

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

Aieee! :-)

 K.

On 15/09/2010 08:10, "Sheng Yang" <sheng@xxxxxxxxxxxxxxx> wrote:

> There is an errata in some of Intel processors.
> 
> AAJ72. EOI Transaction May Not be Sent if Software Enters Core C6 During
> an Interrupt Service Routine
> 
> If core C6 is entered after the start of an interrupt service routine but
> before
> a write to the APIC EOI register, the core may not send an EOI transaction (if
> needed) and further interrupts from the same priority level or lower may be
> blocked.
> 
> This patch fix this issue, by checking if ISR is pending before enter deep Cx
> state. If so, it would use power->safe_state instead of deep Cx state to
> prevent 
> the above issue happen.



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